1. Field of the Invention
The present invention relates to electronic devices and, in particular, to electron-beam tubes.
2. Background Art
Known in the art are electron-beam valves wherein the cathode is a cylindrical tablet and an additional electrode whose potential is higher than that of the anode is accommodated between the cathode and anode (cf., for example, USSR Inventor's Certificate No. 367,482, Class HO1j 21/10, published in Inventions, Discoveries, Industrial Designs, Trade Marks Bulletin, No. 8, 1973).
The design of such valves permits commutation of voltages up to several hundred kilovolts and the efficiency is fairly high. But such valves produce an electron beam from a limited emission surface of the cathode and this is a restriction beyond which the power of valves cannot be increased to the order of several tens of megawatts.
One possibility of providing devices rated for greater power is the use of a multibeam principle for an electron-optical system featuring extended emission cathode surfaces.
Known in the art are electron beam tubes comprising several components coaxially arranged in succession one after another in the direction of the electron flux: a cathode, a control electrode made as a bunch of rods, and a chamber anode whose chambers are formed by the ribs and the bottom located opposite the emitting portions of the cathode (cf., for example, USSR Inventor's Certificate No. 291,607, Class HO1j 21/10, published in Discoveries, Inventions, Industrial Designs, Trade Marks Bulletin, No. 29, 1976).
In such tubes the cathode is assembled around a cylindrical base and is provided with emitting areas which are surfaces of cylindrical rings, the width of each disc electron beam from cathode to anode being constant. With this design the size of the input slot of the anode chamber cannot be significantly increased since it cannot exceed the width of the electron beam on the cathode. In this connection the distance from the butt ends of the anode chamber ribs to the control grid (electrode) is approximately equal to the distance from the control grid to the cathode. The maximum permissible operational voltage and the efficiency of such tubes are substantially limited. If the operational voltage is increased by extending the distance from the anode to the control grid, the current in the tube drops and, consequently, the power is reduced too.